Prior to processing or shipping to market, fresh produce often must be graded or sorted by size. For example, pieces might be sorted into small, medium, and large sizes. Many devices exist to accomplish this sorting. In one type, the produce is fed over openings or spaces of various sizes. If the pieces are smaller than the spaces, they drop through, while larger pieces do not. Generally the produce is advanced over the spaces in order from the smallest to largest spaces, so that the smallest pieces drop out first. The produce may be collected in bins beneath the openings, carried away by conveyor, or removed by some other means.
Often the apparatus consists of a series of parallel rods, rollers, or spindles. The slots between the rods provide the sizing spaces. The produce travels over the rods in the longitudinal direction of the rods and falls through the spaces between the rods. To move the produce over the rods, the rods may be sloped so that the produce travels by gravity. Alternatively or additionally some rods rotate and have a helical rib on their surfaces to advance the produce. An apparatus of this type is shown in the U.S. Pat. No. 3,770,123 to Mraz. A further alternative is to employ apparatus which is vibrated to move the produce along the sizing space defining structure, as in the U.S. Pat. No. 1,927,405 to Johnson. In the U.S. Pat. No. 3,151,742 to O'Brien the produce is carried by a conveyor with only one size of sizing spaces. At one end of the conveyor's loop, a finger belt lifts out the produce that was too large to fall through the sizing spaces in the conveyor.
To provide several sizes of spaces, the sizing rods sometimes diverge, as shown in Johnson. In Mraz, the different sizing spaces are formed by rods that are stepped in diameter.
It has been found that some varieties of produce get stuck or jammed between rods such as those in Mraz or Johnson. This is particularly true of long, thin, twisted produce, such as certain types of peppers. Also, if the produce is dumped in a heap on the apparatus, larger pieces underneath may become jammed between the spacing rods and/or block smaller pieces from the openings.
The spaces between the rods are sometimes adjustable to accommodate different types and sizes of produce. For example, in Mraz, every other rod is adjustable to change the size of the opening. However, in Mraz, the adjustable rod, swung about an axis, does not remain on a level with the fixed roller. This may promote jamming if a piece gets caught underneath the upper roller. In the U.S. Pat. No. 1,832,035 to Leib, the rollers are adjustable horizontally, but each space must be adjusted individually and only when the machine is stopped. In Vance, U.S. Pat. No. 3,108,691, every other rod is laterally adjustable.